I am new comer to Networking. Recently I joined N+ Course so am little aware of networking. Anyone can suggest good book on Networking (LAN,WAN and Internet) troubleshooting.

Previouslly My pc connected to LAN as client (workstation) . Now it is not connected to LAN. Is it problem with server or any changes made in PC can make it disconnect from Server ? How to identify the problems ?

You don't learn troubleshooting from books.. You learn it from either experience or from ground up (starting with basic electricity and going all the way up to OS and sotware design).

"not connected to LAN" means what? If there's no cable attached, then that's your problem

Do you have a link light (a LED next to the network port)?
Do you have a sensible IP address?
Can you ping anything?
Do you see any entries in the ARP cache (after trying to ping)?

What exactly doesn't work?

Thanks Nodsu

not connected to LAN" means what? If there's no cable attached, then that's your problem
Cable is attached.

Do you have a link light (a LED next to the network port)?
Yes, LED light next network port blinking.

Do you have a sensible IP address?
Can you ping anything?
Yes, IP address for PC is 192.162.1.34
When I ping 192.162.1.34 it shows conectivity.

Do you see any entries in the ARP cache (after trying to ping)?
I do not know how to check entries in the ARP Cache. Can you help me ?

try pinging another pc on the network or the router.

Run "arp -a" from command line to see the cache contents. And yes, pinging your own IP address doesn't give you much.